High temperature lubricant composition



HIGH TEMPERATURELUBRICANT COMPOSITION John E. Koch, Jr., Bayonne, N.J., assignor to Celanese Corporation of America, New York, N.Y., a corporation of Delaware,

No Drawing. Filed Apr. 23, 1959, Ser. No. 808,325

. 17 Claims. (Cl. 252-4945) v of the useful energy going into the propulsion of the aircraft Jetturbine bearings are lubricated by pumping a lubricant to .the bearings from a reservoir in a closed. system- The design of more, powerful jet turbines has led to an increase in' the lubricant reservoir temperature and to greater difficulty. in maintaining lubricant stability under the more severe conditions. For example, a lubricant which will'operate satisfactorily at a reservoir-terniv v United States atent perature of 250 F. will sludge badly, build up viscosity, develop high acidity and corrode metals at a reservoir temperature of 400 F.

Carboxylic acidesterafsuch as esters' of polyols with alkanoic acidsare useful as lubricants and esters of poly-v ols, such astriinethylolpropane, trimethylolethane and pentaerythritol," which have at least two methylol groups bonded to a quaternary carbon atom are particularly useful for good oxidative. and. thermal stability. However, even these compounds are not" stable under oxidative conditions in a system ,where the reservoir temperature is 'of the order of 400,F. and the local temperature at the bearings may be as high as600 to 700 F.

It is an object of this invention to provide a lubricant composition whichwill withstand oxidative conditions at temperatures of the orderof 425 F. and higher, for

extended periods witho'utY-substantial degradation.

It is a further object of this invention to provide at additive composition; which can enhance the oxidative stability 'of'polyol esters to, the. desired degree.

The objects of this invention are achieved by provid- The polyol esters are esterificationproducts of single alkanoic acids, or mixtures of alkanoic, acids, with a polyol having atleast two, and preferably three, methylol groups one. quaternary carbon atom. Among the polyols which may be used are trimethylolpropane, trimethylolethane, neopentyl glycol, pentaerythritol, 2butyl-2-ethyl- 1,3-propanedio'l and 2,2,4-trimethyl-1,3-pentanediol.

The alkanoic acids used to make the polyol esters have average chains of at least 5 carbon atoms and preferably from 5 to 8 carbon atoms. The individual acids, where mixtures are used may range in chain length from 2 12 carbon atoms. Normal acids are preferred, althoug branched alkanoic acids may also be used, particular those with no more than two carbon atoms in side chain The polyol esters are prepared by the esterification t the polyol in the'presence of a slight excess of alkano acid, either in the presence or in-the absence of an acid catalyst. For optimum heat stability, it is preferred carry out the reaction in the absence of a catalyst. Whe: a catalyst is used, it is generally used in an amount b tween about 0.05 and about 1.0 percent, based on tl weight of the reactants. The preferred catalysts are 1 toluene sulfonic acid, benzene sulfonic acid, zinc salt lead salts, and related materials.

The 'esterification temperature .is preferably betwee about 180 and about 240 C. and the reaction peric may suitably range from about 6 to about 18 hour Water isremov'ed by volatilization, preferably in ti presence of an azeotroping agent, such as a liquid hydrt carbon. v

The diaromatic secondary amines include diaryl amine aryl-alkaryl amines and dialkaryl. amines, with the arj groups preferably having no more than 5 benzene ring and the alkyl substituents, when present, having no mo: than 24 carbon atoms. Among the specific diaromat secondary amines which may be used are phenyl a nap] thylamine, p,p' dioctyldiphenylamine and phenyl B napl thylamine.

The diaromatic secondary amine is suitably used i amounts between about 0.25 and about 3% by weigh based on the polyol ester and most preferably in amoun This compound may be prepared from N-ethyl diphen; amine by first reacting one mol of the latter with tw moles of butyl lithium (at C. with a nitrogen purg to sweep out the butane by-product) to produce 2,2 dilithium-N-ethyl diphenylamine and then reacting th last named compound (at 180-220 C.) with an eqtr molar proportion of diphenyl dichlorosilane to produc the desired compound.

Another method of preparationinvolves the reactio. of N-ethyl phenothiazine with diphenylsilane in equimola proportions to produce the desired compound with hydrc gen sulfide as a by-product.

Other phenosilazine derivatives which may be use include phenodiphenyl silazine, N-methyl-phenodipheny silazine, N-isopropyl-phenodiphenyl silazine, N-ethyl phenoditolyl silazine and N-ethyl-phenodinaphthyl sila zine, bis-N-ethyl phenosilazine, and his compounds 0 the other derivatives mentioned above.

The phenosilazine derivative is suitably used in amount between about 0.25 and about 3% by weight, based 0: the pol'yolesterand most preferably in amounts betweei about 0.5 and about 2% by weight.

.It has been found that a-combination of the two com aundsprodudes substantially better inhibition of vissitybuildup4and of acidity development than either rmpound'a-lone, even when'used in equivalent amounts.

4- Examples 11 to VIII The trihept'anoate esters of Examples Ia and lb, were blended with-N-ethyl-phenodipheny1 silazine and phenyl a-naphthylamine in the proportions shown in the table below. The'N ethyl-phei'iodiphenylsilazine wasdissolved, with stirring, after heatingthe ester to 200 F. and the phenylpz-napht-hylamine was dissolved while cooling the teory," it is believed that each of the compounds complerents the action of the'othei'. to provide the desired 'otection. 1 It is believed; that thephe'nosilazine lderivaester back to room temperature. Each blend. in a 1100 ml. sample,'was.'heated in a glass tube to the temperature shownin .thetable while dried air at, a rate of 5 1./hr. was blownthrough the sample. One inch square metal platelets'labout0.032 inch thick) were suspended in the blends and weighed before and after exposure to determine corrosion. Plat'elets of' steel, copper, aluminum, titanium V8 fullfitidns as an -l y a i f i p and silver wereused except in the case of Example II [res referred to above, and is incapable of retarding Where onlysteel was used. The tests were run for tidation at low and intermediate*temperatures. It is hours. Example N0 It; III IV V VI VII VIII 'Estero'fExanipl---;.' r..- 'Ib n. I11 1.1 lb Ia. .Pero'ent N-ethyl-phenodiphenyl silazine 1.0 '1.5 1.0 1.0 1.0 1.0 1.0 Percent P-henyl a-naphthylamine 1-,0 0.5 1. 0 1.0 1. 0 1.0 1.0 .TempeI8tiIreS,j 3F 500 g -.500 500 400 400 450 450 Acidity, Mgs. KOH per gm 9. 8 12.7 7.4 0.39 0. 23 3. 39 2. 49 Visgosity' cs. 100 F 22.63 21.57 21. 85- 16.69 16.57 17.14 18. 02

hang'ei weight of metal specimens, rugs/cm):

Steel. -7 +0.09 +0.10 +0.19 +0.04 +0.03 +0.08 N.C. +0.81 -0. 54 -0. 09 -0. 0e -0. 45 0. 23 +0.-12 +0. 14 +0. 05 +0. 01 +0. 03 -0. 01 +0. 11 +0. 09 +0. 06 +0. 03 +0.02 N.O. +0.09 +0.12 +0.05 +0.03 +0.05 -0.02

so believed that the phenosilazine derivatives .are xrela-. 'ely ineffective even at high temperatures once acidity scription is merelygive'n'by wayof illustration and that LS started to'build up. The secondary: amine; which itself is incapable of retarding oxidationat high tern matures, Serves to retard. oxidation and-acidity buildup cing the warming and cooling periods and permits the" i'enojsilazine derivativeto operate at its iulljeffectiveness the higher temperature.- The 'phenosilazine derivatives and these'condary amines ay be advantageously blended together, in the desiredoportion to produce a. combinatio'naddi'ti'y el] Or eachay be'se'parately dissolved injthe ,polyohester with the It is to beuriderstood that;the-foregoing detailed'demany variations may helmad therein without departing from the spirit of my invention.

Having described my invention, what I desire to secure by Letters Patent is:

4 l. A high temperature lubricant comprising a major proportion of a normally liquid'alkanoic acid ester of a lenosilazine' derivative generallyfbeing dissolved-at a pound having a phenosilazine ring. having its nitrogen valence satisfied bya member of the groupconsisting of polyol having two to four methylol groups on a quaternary carbon atom. saidalkanoic acid having an average of at least 5 carbon atonsandfthe individual acids of which contain 2 to 12- carbon atoms, said ester being stabilized against high temperature oxidati ve degradation by a minor proportion of a diaro'matic secondary amine selected from the group consisting-of diaryl amines, aryl alkaryl amines and di alkaryl ar'ninesand aininor proportion of acomhydrogen and lower alkyl radicals and its silicon valences bonded to aromatic rings. I

-'2.A high temperature lubricant comprising a major proportion of a normallyiliquidalkanoic acid ester of a .5.h'ours with the-maximum temperature in the-reaction ui'drising to 242 C. At the end .o'f'theheating" period e naphtha was flashed off. The mixture-was-then dispolyol having three methylol groups on a quaternary carbon atom. said alkanoic acid having an average of at least 5 carbon atoms and the individual acids of which contain led at an'absolu'te pressure of Hg and the fr'ac- Pl'l coming'ofi at a vapor temperature of 255-281 C. lS- collected. The collected materialwas giveriian alkale wash and a water wash and then The finishedvv nie'thylolpropane triheptanoate had .a specific gravity 0/20) of 0.963, an acid number (mg, KOH/g.) of 0.04, hydroxyl content of 0.20 weight-percent and a water mainof 0.0] weight percent,

(b) Another batch of trimethylolpropane triheptanoate v lS- prepared by a procedure essentially similar to that scribed above except that the toluenesulfonic acid was iittedin the reaction and that the distillation step was iitted. The product had a specific gravity (20/20) of 964, an acid number (mg. KOH/g.) of 0.01 and a water ntent of 0.01 weight percent.

2 to 12 carbon atoms, said ester being stabilized against high temperature oxidative degradation by a minor prolportion of a diaromatic secondary amine selected from the group consisting of diarylj amines, aryl alkaryl amines and di-alkaryl amines and a minor proportion of "a com pound having a phenosilazine ring having its nitrogen valence satisfied by a member of the group consisting of *hydrogen and lower alkyl radicals and its silicon valences bondedto aromatic rings.

.3; A high temperature-lubricant comprising a major proportion of an alkanoic acid ester of trimethylolpropane, said alkanoic acid having an average of from 5 to 8 carbon atoms, said ester beingstabiliz'ed against high temperature oxidative degradation by a minor proportion of a diaromatic secondary amine selected from the group consisting of diaryl amines, aryl alkaryl amines and dialkaryl amines and a minor proportion of a compound having a phenosilazine ring having its nitrogen valence sat isfied by a member of the group consisting of hydrogen and lower alkyl radicals and its silicon valences bonded to aromatic rings.

4. A high temperature lubricant comprising a major Q proportion of trimethylolpropane triheptanoate, said trimethylolpropane triheptanoate being stabilized against high temperature oxidative degradation by a minor proportion of .a diaromatic secondary amine selected from the group consistinggof diary-l amines, aryl alkaryl amines and di-alkaryl-amin'esand a minor proportion of a compound having a phenosilazine ring having its nitrogen v lence satisfiedibya member of the group consisting of.

hydrogen and lower alkyl radicals and its silicon valences bonded to aromatic rings.

5. A high temperature lubricant-comprising a major proportion of .:a normally liquid, alkanoic acid ester of a polyol having two tofour methylol groups on a quaternary carbon atom, s'aidalkanoic acid'havingan average of at least 5 carbon at'oms and the individual acids of which contain 2. to 121ca1ihon atoms, said ester being stabilized against high temperature oxidative degradation by a minor proportion of adiaromatic secondary amine selected from the group consisting of diaryl arnines, aryl alkaryl amines and di-alkaryl amines and aminor proportion of an N'- alkyl-phenodiphenyl silazine.

i said alkanoic acid having an average of from 5 to 8 c bon atoms, said ester being stabilized against high te perature oxidative degradation by from 0.25 to 3 wei percent of phenyl ot-naphthylamine and from 0.25 tc weight percent of N-ethyl-phenodiphenyl silazine.

11. The lubricant of claim 1, wherein said diaromz secondary amine is present in an amount between abt 0.25 and 3 weight percent and said phenosilazine co pound is present in an amount between about 0.25 and weight percent.

12. A high temperature lubricant comprising a ma; proportion of trimethylolpropane triheptanoate, said 1 methylolpropane triheptanoate being stabilized agaii high temperature oxidative degradation by from abc 0.5 to about 2 weight percent of phenyl e-naphthylami and from about 0.5 to about 2 weight percent of N-eth pheno'diphenyl silazine. e

13. An anti-oxidant composition consisting essential of a diaromatic secondary amine selected from the grow consistingod diaryl amines, aryl alkaryl amines and alkaryl amines and a compound having a phenosilazi ring having its nitrogen valence satisfied by a member the group consisting of hydrogen and lower alkyl radica and it's' silicon valences bonded to aromatic rings, sa components being present in a weight ratio of 0.25

Y to 3:0.25.

6. A high. temperature lubricant comprising a' majoreonsisting of diaryl amines, aryl alkaryl amines and c proportion ofa normally liquid alkanoic acid ester ottri- I methylolpropan'e, said alkan'oic'acidhaving an average of contain 2 to 12 carbon atoms, said ester being stabilized i at least 5 carbon atoms and the individual acids of which? against high temperature oxidative degradation by a; minor proportion of a diarom'atic secondary amine selected I from the groupconsisting of diaryl amines, aryl alkaryl amines and di-alkaryl amines and a minor proportion of an N-alkylphenodiphenyl silazine.

7. A high temperature lubricant comprising a major proportion of a normally liquid alkanoic acid ester of a;

polyol having two tofour' methylol groups on a quaternary against high temperature oxidativefdegradation by a minor proportion of a diaromatic secondary amine selected from the group consistingof diaryl amines, aryl alkaryl amines and di-alkar'yl' amines and a minor'proportion of N-ethylphenodiphenyl sila'z'ine.

14. An anti-oxidant composition consisting essential of a diaromatic secondary amine selected from the grot alkaryl-amines and a phenosilazine compound having tl structure wherein the nitrogen valence is satisfied by a member the group consisting of hydrogen and lower alkyl radica and the silicon valences are bonded to aromatic ring 3 said components being present in a weight ratio of 0.25:

8. A high temperature lubricant comprising a major.

proportion of analkanoic acid ester. of a polyol having two to four methylolgroups on a quaternary carbon atom,..

said alkanoic acid having an average of from 5 to 8 carbon atoms, saidester being stabilized against high temperature oxidative degradation by a minor proportion of phenyl a-naphthylamine and a minor proportion of a 4 15. An anti-oxidant composition consisting essential] of phenyl a-naphthylamine and a compound having 'phenosilazine ring having its nitrogen valence satisfie .by a member of the group consisting of hydrogen an lower alkyl radicals and its silicon valences bonded t aromatic-rings, said components being present in a weigl ratio of 0.25:3 to 3:025.

16. An anti-oxidant composition consisting essential] of a diaromatic secondary amine and N-ethyl-phenod lubricants consisting essentially of phenyl a-naphthylamin compound havinga phenosilazine ring having its nitrogen valence satisfied by a member of the group'consisting of hydrogen and lower alkyl radicals and its silicon valences bonded to aromatic rings.

9. A high temperature lubricant comprising a major proportion of an alkanoic acid ester of a polyol having two to four methylol groups on a quaternary carbon atom, said alkanoic acid having an average of from 5 to 8 carbon atoms, said ester being stabilized against high temperature oxidative degradation by a minor proportion of phenyl phenyl s'ilazine in a weight ratio of 0.25:3 to 3:025.

17. An anti-oxidant composition for carboxylic este and N-ethylphenodiphenyl silazine in a weight ratio fror a-naphthylamine and a minor proportion of N-ethylphenodiphenyl silazine.

10. A high temperature lubricant comprising a-major proportion of an alkanoic acid ester of trimethylolpropane,

References Cited in the file of this patent FOREIGN PATENTS Great Britain Apr. 6, 194

OTHER REFERENCES ion in Interference 3,036,005 J. E. Koch J12,

0. 93,833 involvingiPatent N0 NT coMPoslTlN, final ]udg- In Interference N BRIG HIGH TEMPERATURE LU ment adverse to the patentee was r 12 and 17 [bfficial Gazette June %8, 1.966.]

endered Dec. 20, 1965, as to claims 9, 10, 

1. A HIGH TEMERATURE LUBRICANT COMPRISING A MAJOR PROPORTION OF A NORMALLY LIQUID ALKANOIC ACID ESTER OF A POLYOL HAVING TWO TO FOUR METHLOL GROUPS ON A QUATERNARY CARBON ATOMS, SAID ALKANOIC ACID HAVING AN AVERAGE OF AT LEAST 5 CARBON ATOMS AND THE INDIVIDUAL ACIDS OF WHICH CONTAIN 2 TO 12 CARBON ATOMS, SAID ESTER BEING STABILIZED AGANIST HIGH TEMERATURE OXIDATIVE DEGRADATION BY A MINOR PROPORTION OF A DIAROMATIC SECONDFARY AMINE SELECTED FROM THE GROUP CONSITING OF DIARYL AMINES, ARYL ALKARYL AMINES AND DI-ALKARYL AMINES AND A MINOR PROPORTIONS OF A COMPOUND HAVING A PHENOSILAZINE RING HAVING ITS NIROGEN VALENCE SATISFIED BY A MEMBER OF THE GROUP CONSISTING OF HYDROGEN AND LOWER ALKYL RADICALS AND ITS SILICON VALENCES BONDED TO AROMATIC RINGS. 